Resonant transmission through an open quantum dot

We have measured the low-temperature transport properties of a quantum dot formed in a one-dimensional channel. In zero magnetic field this device shows quantized ballistic conductance plateaus with resonant tunneling peaks in each transition region between plateaus. Studies of this structure as a function of applied perpendicular magnetic field and source-drain bias indicate that resonant structure deriving from tightly bound states is split by Coulomb charging at zero magnetic field.Comment: To be published in Phys. Rev. B (1997). 8 LaTex pages with 5 figure

ortho-Quinone methide cyclizations inspired by the busseihydroquinone family of natural products

A series of cascade reactions of o-quinone methides have been developed based on the proposed biosynthesis of busseihydroquinone and parvinaphthol meroterpenoid natural products. The polycyclic framework of the most complex family members, busseihydroquinone E and parvinaphthol C, was assembled by an intramolecular [4 + 2] cycloaddition of an electron-rich chromene substrate. The resultant cyclic enol ether underwent rearrangements under acidic or oxidative conditions, which led to a new total synthesis of rhodonoid D.Laura Burchill, Henry P. Pepper, Christopher J. Sumby, and Jonathan H. Georg

Measurement of the electron phase relaxation rate in In0.53Ga0.47As: a possible diagnostic test of compositional disorder

The authors present low-field magnetoresistance measurements made at low temperatures (<or=4.2K) on n-type samples of the semiconductor alloy In0.53Ga0.47As doped in excess of the metal-insulator transition. The samples were strongly degenerate at the temperatures of the measurements. The low-field magnetoresistance is found to be governed by quantum interference (weak-localisation) effects. The authors find that good fits to the data are obtained with a phase relaxation time as the sole variable. This time is much shorter than the calculated magnetic or spin-orbit scattering times, supporting their assertion that these are only minor perturbations

Indoor air-quality measurements in energy-efficient residential buildings

The potential impact on indoor air quality of energy-conserving measures that reduce ventilation is being assessed in a field-monitoring program conducted by the Lawrence Berkeley Laboratory. Using a mobile laboratory, on-site monitoring of infiltration rate, carbon dioxide, carbon monoxide, nitrogen dioxide, nitric oxide, ozone, sulfur dioxide, formaldehyde, total aldehydes, and particulates was conducted in three houses designed to be energy-efficient. Preliminary results show that energy-conserving design features that reduce air-exchange rates compromise indoor air quality; specifically, indoor levels of several pollutants were found to exceed levels detected outdoors. Although the indoor levels of most pollutants are within limits established by present outdoor air-quality standards, considerable work remains to be accomplished before health-risk effects can be accurately assessed and broad-scale regulatory guidelines revised to comply with energy-conservation goals

Endothelial cells of the microvasculature express epidermal fatty acid-binding protein (E-FABP)

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Investigations of electron-beam and optical induced damage in high mobility SiGe heterostructures

Modulation-doped two dimensional electron gases (2DEGs) grown on Si0.7Ge0.3 virtual substrates were investigated. Low temperature measurements were used to characterise the uniformity of the wafers and annealing studies demonstrated that high annealing temperatures (above 600°C) destroyed the electrical properties. Studies of excimer irradiation of the 2DEG material demonstrated that only surface damage was induced, but the subsequent annealing of this damage reduced the carrier density in the material, suggesting strain relaxation of the strained Si cap. Electron beam irradiation experiments at 40 keV and PMMA doses showed charging effects at room temperature but little damage. Finally a number of narrow channel devices were fabricated using 300 keV electrons and characterised at low temperature to estimate the range of the electron-beam induced damage